Electrical switching devices such as relays and circuit breakers are often encapsulated in cases to protect the operating mechanisms from dust, moisture and other environmental conditions, and to prevent technicians and others from contacting live electrical parts. Certain operating conditions may cause a blast or build-up of hot, pressurized gases and other materials within the case. For example, short circuits may cause contacts in relays or circuit breakers to melt or explode, thereby releasing hot gases and molten metal. As another example, an over current condition may cause the contacts in a circuit breaker to open, which may in turn, create a momentary arc between the contacts. The arc releases a blast of ionized air.
If the blast is not vented from inside the case, it may damage, destroy or interfere with the operation of the electrical device and/or cause the case to rupture, thereby scattering dangerous blast products which can, in turn, cause a fire and/or create an electrical shock hazard. Thus, cases for electrical switching devices are often provided with a vent in the top or side of the case to enable a short circuit or other type of blast to escape from within the case. While venting the case may solve certain problems with the electrical switching device, it often causes other problems. For example, in an electrical enclosure housing multiple components, a blast from one device may be directed at another device, which in turn is damaged or destroyed by the blast. In addition, within the electrical switching device, the blast can short high voltage terminals with low voltage circuitry, creating a potential hazard.
Some other previous efforts to accommodate a blast from an electrical switching device have involved the use of complicated systems of baffles or dividers between components to direct the blast from one component away from other components. These systems, however, add cost and complexity, and may still create hazardous conditions.